Sliding Surface of Sliding Member

ABSTRACT

Convex portions are formed by directly quenching the sliding surface of the sliding member in a line shape or a dot shape, and concave portions are formed in indirectly quenched portions adjacent to the directly quenched portions, whereby an irregular surface is formed on the sliding surface by the directly quenched portions and the indirectly quenched portions. The directly quenched portions are formed in a lattice shape, a parallel straight line shape, a concentric circle shape or a spiral shape. By forming the irregular surface on the sliding surface by the directly quenched portions and the indirectly quenched portions, the seizure resistance can be improved.

TECHNICAL FIELD

The present invention relates to a sliding surface of a sliding member such as a semispherical shoe and, more particularly, to a sliding surface of a sliding member in which the seizure resistance is increased by improving the sliding surface thereof.

BACKGROUND ART

Conventionally, various types of sliding members have been known, and as a sliding member used under severe conditions, a semispherical shoe used for a swash plate compressor has been known.

The semispherical shoe has a semispherical surface having a semispherical shape and a smooth end surface. The semispherical surface comes into slidable contact with a semispherical concave portion of a piston forming the swash plate compressor, and the end surface comes into slidable contact with a swash plate provided on a rotating shaft. That is to say, the semispherical shoe is configured so that the semispherical surface serves as a sliding surface with respect to the piston, and the end surface serves as a sliding surface with respect to the swash plate.

The sliding surface of the semispherical shoe is usually manufactured so as to be smooth with a roughness not higher than the required value (Patent Document 1). Patent Document 1: Japanese Patent Laid-Open No. 2001-153039

DISCLOSURE OF THE INVENTION Issues to be Solved by Invention

The semispherical shoe is required to have high seizure resistance. The reason for this is that in particular, the end surface that comes into slidable contact with the swash plate has a difficulty of being sufficiently supplied with a lubricating oil because the lubricating oil is supplied while being contained in a refrigerant, fluctuations in pressing force to the swash plate caused by the reciprocating motion of piston are large, and moreover the end surface is momentarily brought into contact with the swash plate under a considerably high pressure.

The present invention has been made in view of the above circumstances, and accordingly an object thereof is to provide a sliding surface of a sliding member, in which the seizure resistance of the sliding surface of the sliding member such as a semispherical shoe that is required to have high seizure resistance is further improved.

Means to Solve the Issues

The invention of claim 1 provides a sliding surface of a sliding member, characterized in that convex portions are formed by directly quenching the sliding surface of the sliding member in a line shape or a dot shape, and concave portions are formed in indirectly quenched portions adjacent to the directly quenched portions, whereby an irregular surface is formed on the sliding surface by the directly quenched portions and the indirectly quenched portions.

EFFECT OF INVENTION

According to the invention of claim 1, since the irregular surface is formed on the sliding surface of the sliding member by the directly quenched portions and the indirectly quenched portions, as shown by the later-described experimental result, high seizure resistance can be ensured as compared with the conventional sliding surface of the sliding member having no such an irregular surface.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be explained with reference to examples shown in the accompanying drawings. In FIG. 1, a semispherical shoe 1 serving as a sliding member is used for a conventionally well-known swash plate compressor, and is interposed between a swash plate provided tiltingly on a rotating shaft not shown and a semispherical concave portion provided in a piston so that the piston can be reciprocatingly driven with the rotation of the swash plate.

The semispherical shoe 1 has a semispherical surface 2 having a semispherical shape and a smooth end surface 3, and is configured so that the semispherical surface 2 is in slidable contact with the semispherical concave portion in the piston, and the end surface 3 is in slidable contact with the swash plate. Also, in the central portion of the end surface 3, an oil reservoir 4 consisting of a concave portion is formed.

In an example shown in FIG. 2, lattice-shaped convex portions 3 a are formed on the end surface 3, and portions other than the convex portions 3 a relatively become concave portions 3 b, by which an irregular surface is formed on the end surface 3.

The convex portions 3 a are formed by directly quenching the end surface 3 by the irradiation of laser. Specifically, as shown in FIG. 3, in the portions irradiated with the laser, a base material surface 3 c originally forming the surface of the end surface 3 becomes in a directly quenched state and expands from the base material surface, by which the convex portions 3 a are formed.

Although the portions irradiated with the laser become in a directly quenched state, the concave portions 3 b that are located adjacent to the portions irradiated with the laser and are not irradiated with the laser are not quenched directly, and become indirectly quenched portions. These indirectly quenched portions are recessed relative to the convex portions 3 a, and therefore the concave portions 3 b are formed.

However, this does not mean that the concave portions 3 b, which are indirectly quenched portions, are not quenched completely. Specifically, since the range quenched by laser irradiation has a semicircular shape in cross section with the laser irradiation position being the center, for example, as indicated by an imaginary line 5 in FIG. 3, by narrowing the adjacent laser irradiation intervals, the concave portions 3 b, which are indirectly quenched portions at intermediate positions of the intervals, can also be quenched. Whether the concave portions 3 b, which are indirectly quenched portions, are quenched or not can be determined by the setting of the laser irradiation intervals. If the concave portions 3 b, which are indirectly quenched portions, are quenched, those portions expand from the base material surface 3 c though not so much as the convex portions 3 a.

Next, the experimental result of seizure resistance is explained.

In this experiment, YAG laser was applied to the end surface 3 of the semispherical shoe 1 manufactured of SUJ2 straightly and in parallel at intervals of 0.2 mm, and then was applied in the perpendicular direction in parallel at intervals of 0.2 mm; as a whole, YAG laser was applied in the lattice form. The interval is preferably in the range of 0.1 to 0.3 mm.

The output of the YAG laser was 50 W, and the condenser lens was adjusted so that the YAG laser is in focus at a position of a 2 mm depth with respect to the surface of the end surface 3. Therefore, the YAG laser was applied to the surface of the end surface 3 in a defocused state.

The surface of the convex portion 3 a, which is a directly quenched portion irradiated with the laser, had a hardness about Hv100 higher than the hardness of the base material, which is Hv750, and also the surface of the concave portion 3 b had a hardness increased by about Hv50. On the other hand, a portion 6 (refer to FIG. 3) slightly deeper than the directly quenched portion was quenched so that the hardness thereof was about Hv100 lower than the hardness of the base material. Also, an intersection of the convex portion 3 a and the convex portion 3 a, which are directly quenched portions, namely, a portion in which the laser irradiation portions intersect was also quenched so that the hardness thereof was likewise about Hv100 lower than the hardness of the base material. However, since the quenching using laser involves rapid cooling, a decrease in hardness of base material was not recognized at a position still deeper than the slightly deep portion 6.

After being irradiated with the laser as described above, the end surface 3 of the semispherical shoe 1 is completed by being subjected to lapping and buffing in succession. The height of the convex portion 3 a with respect to the concave portion 3 b is about 0.1 to 10 μm immediately after the laser treatment, and the height thereof of the completed product after the lapping and buffing is preferably in the range of 0.1 to 1 μm.

The wear resistance was measured under the following test conditions on the invented product manufactured as described above and the reference product subjected to lapping and buffing under the same conditions without being irradiated with laser. For the reference product, the whole of the semispherical shoe was quenched, and the hardness thereof was Hv750.

Rotational speed of swash plate: increased in nine steps every one minute by 1000 rpm: the maximum rotational speed 9000 rpm (circumferential speed 38 m/s)

Surface pressure: increased every one minute by 2.7 MPa from a preload of 2.7 MPa: up to seizure

Quantity of oil mist: 0.05 to 0.25 g/min nozzle position fixed

Oil: refrigerating machine oil

Seizure condition: shaft torque 4.0 N·m over

That is to say, the rotational speed of the swash plate was increased under the above-described condition in the state in which the end surface of the invented product was brought into contact with the swash plate under pressure. On the other hand, the surface pressure at the time when the invented product was brought into contact with the swash plate under pressure was increased under the above-described condition. When the shaft torque applied to the swash plate exceeded 4.0 N·m, it was judged that seizure occurred. The same test was also conducted on the reference product.

As seen from the experimental result shown in FIG. 4, the invented product provides significantly high seizure resistance as compared with the reference product.

FIGS. 5 to 8 show other examples of the present invention. In FIG. 5, the convex portions 3 a are formed by forming the directly quenched portions in a parallel straight line shape, and the concave portions 3 b are formed in the indirectly quenched portions adjacent to the directly quenched portions, by which the irregular surface is formed on the sliding surface by the directly quenched portions and the indirectly quenched portions.

Also, in FIG. 6, the convex portions 3 a are formed in a concentric circle shape, and in FIG. 7, the convex portions 3 a are formed in a spiral shape. Further, in FIG. 8, dot-shaped convex portions 3 a are formed on the sliding surface by applying laser to the intersection of lattice shape.

In the above-described examples, the semispherical shoe 1 is used as the sliding member. However, the sliding member is not limited to the above-described examples, and needless to say, the present invention can be applied to various sliding surfaces.

Also, in the above-described examples, the convex portions are formed by directly quenching the sliding surface by laser. However, the quenching method is not limited to laser, and plasma beam etc. can be used.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view showing a first example of the present invention;

FIG. 2 is a bottom view of FIG. 1;

FIG. 3 is an enlarged sectional view of an essential portion, showing in an exaggerated way;

FIG. 4 is a graph showing the experimental result of seizure resistance;

FIG. 5 is a bottom view showing a second example of the present invention;

FIG. 6 is a bottom view showing a third example of the present invention;

FIG. 7 is a bottom view showing a fourth example of the present invention; and

FIG. 8 is a bottom view showing a fifth example of the present invention.

DESCRIPTION OF SYMBOLS

-   1 semispherical shoe (sliding member) -   3 end surface (sliding surface) -   3 a convex portion -   3 b concave portion 

1. A sliding surface of a sliding member, characterized in that convex portions are formed by directly quenching the sliding surface of the sliding member in a line shape or a dot shape, and concave portions are formed in indirectly quenched portions adjacent to the directly quenched portions, whereby an irregular surface is formed on the sliding surface by the directly quenched portions and the indirectly quenched portions.
 2. The sliding surface of a sliding member according to claim 1, characterized in that the sliding member is a semispherical shoe, and the sliding surface is the end surface of the semispherical shoe.
 3. The sliding surface of a sliding member according to claim 1, characterized in that the sliding surface is directly quenched by portions irradiated with laser that is applied onto the sliding surface, and the convex portions are formed by the irradiation portions.
 4. The sliding surface of a sliding member according to claim 1, characterized in that the height of the convex portion on the irregular surface is in the range of 0.1 to 10 μm.
 5. The sliding surface of a sliding member according to claim 1, characterized in that the interval of the adjacent convex portions on the irregular surface is in the range of 0.1 to 0.3 mm.
 6. The sliding surface of a sliding member according to claim 1, characterized in that the directly quenched portions are formed in a lattice shape, a parallel straight line shape, a concentric circle shape or a spiral shape. 